Exechonella elegantissima, Cáceres-Chamizo & Sanner & Tilbrook & Ostrovsky, 2017

Cáceres-Chamizo, Julia P., Sanner, Joann, Tilbrook, Kevin J. & Ostrovsky, Andrew N., 2017, Revision of the Recent species of Exechonella Canu & Bassler in Duvergier, 1924 and Actisecos Canu & Bassler, 1927 (Bryozoa, Cheilostomata): systematics, biogeography and evolutionary trends in skeletal morphology, Zootaxa 4305 (1), pp. 1-79 : 50-52

Exechonella elegantissima n. sp.

( Fig. 20 , Table 19)

Material examined. Holotype: DPUV 2012-0006-0001 , on coral rubble (mounted on SEM stub and coated with gold). Red Sea , the Northern Bay of Safaga, west part of Safaga Island, transect A 5, depth 1–2 m, September 1992 . Paratypes: DPUV 2012-0006-0002 , DPUV 2012-0006-0003 (mounted on SEM stub and coated with gold). Red Sea , the Northern Bay of Safaga, station B 3/2, depth 4 m, 16 July 1987 . Other material examined: DPUV collection, non-numbered small fragment (mounted on SEM stub and coated with gold). Red Sea , the Northern Bay of Safaga, south of Ras Abu Soma, depth 1–20 m, September 1992 . MTQ G 100214, on coral (mounted on SEM stub, uncoated). Coral Sea , Great Barrier Reef , Lizard Island, Pigeon Point, depth 8–10 m, 9 October 2012 .

Etymology. The species is named because of its delicate structure with specific elegant peristome and small and scattered foramina. Derived from the Latin word “elegans” (elegant).

Description. Colonies encrusting, unilaminar, multiserial. Autozooids oval, separated by narrow deep grooves. Primary orifice oval, wider than long, with proximal shelf (a distalmost part of the zooidal frontal shield proximally surrounded by a wall of the peristome) with a tiny smooth central projection (sometimes missing in proximal zooids) and wrinkled lateral areas. Anter (distal half of primary orifice) is underlain by an inner lamina that is not visible in frontal view, and which ends form thick and rounded condyles pointed downwards or directed to the orifice midline. Peristome tubular, slightly pustulose externally. Its proximal edge forms a deep and wide Ushaped sinus. Frontal wall convex, gently pustulose, with 9–21 small and widely dispersed foramina. Each foramen is a small and short, cylindrical or conical tube with rounded or slit-like opening. Base of some tubes is surrounded by a ring-like elevated area. Marginal pores small and rounded. Vertical zooidal walls narrow, represented by multiporous mural septula with communication pores arranged in one row. Adventitious kenozooids with 3–5 pores having centrally perforated cuticular plate. Ancestrula and avicularia are unknown.

Northern Bay of Safaga, Red Sea Lizard Island, Great Barrier Reef Remarks. E. elegantissima n. sp. is characterized by its primary orifice with a central projection on the proximal edge, tubular peristome with a deep and wide U-shaped sinus and foramina with a small and short, cylindrical or conical tube.

E. elegantissima n. sp. is reminiscent E. albilitus Tilbrook, 2006 . The main difference is the shape of the peristome that is cylindrical with flared edge in E. albilitus (also having a length 400 µm), and with a proximal sinus (275 µm in length) in E. elegantissima n. sp. The number of frontal foramina (which base is conical and opening 34 µm) ranges between 20 and 30 in the former species, whereas there are of 9–21 foramina developed in the latter, in which most foramina of 18 µm are tube-like without elevated basal area.

The specimens from the Red Sea and Australia totally correspond to each other by both morphology and size.

Distribution. Exechonella elegantissima n. sp. was found in the Red Sea, the Northern Bay of Safaga and in the Coral Sea, northeast Australia, Great Barrier Reef, Lizard Island.

Figures

FIGURE 20. Exechonella elegantissima n. sp. (A ‒ E: MTQ G 100214, Great Barrier Reef, Lizard Island; F, G, holotype: DPUV 2012 - 0006 - 0001, Northern Bay of Safaga). A, general colony view from above. B, C, group of autozooids showing details of peristomes and frontal shields. Two kenozooids shown by arrows in C. D, E, details of primary orifice and peristome. Condyle shown by arrow F, G, lateral view of peripheral colony part showing shape of peristomes and narrow multiporous mural septula. Scale bars: A = 1 mm; B ‒ G = 100 µm.